Property Value

Type: String
A string representaion of the message transfer agent type from "Reporting-MTA" DSN field,
or a null reference (Nothing in Visual Basic) if no such field contained in the DSN.

Remarks

Reporting MTA is the one which is reporting the results
of delivery attempts described in this DSN. Usually, it's either the destination mail server
(the SMTP MX server which accepts mail for the domain of the recipient e-mail address)
or the sending e-mail server if the destination mail server could not be contacted
(for instance, the recipient domain is invalid).

In this example, DSN field is:
Reporting-MTA: dns; host.home.local
The return value is marked bold.